Air return system for air feed drill



July 20, 1965 T. s. REED ETAL AIR RETURN SYSTEM FOR AIR FEED DRILL FiledJuly 25, 1962 2 Sheets-Sheet l FIG 2 July 20, 1965 T. s. REED ETAL AIRRETURN SYSTEM FOR AIR FEED DRILL Filed July 25, 1962 2 Sheets-Sheet '2 MM. a a mi# m wmw ww mmm MW United States Patent 3,195 658 AIR RETURLJSYSTEM iFfiR AIR FEED DRTLL Thomas S. Reed, Athens, Pa, and Hugh E.Taylor, Wa-

verly, N.Y., assignors to lngersoll-Rand Company, New York, N.Y., acorporation of New Jersey Filed July 25, 1962, Ser. N 212,207 Claims.(Cl. 173-158) This invention relates to fluid pressure-operated toolswhich simultaneously rotate and axially reciprocate a tool implement. Anexample of this type of tool is the air feed drill disclosed in thecopending US. patent application of John M. Clapp et al., Serial No.201,852, filed June 12, 1962, now abandoned.

Generally, it is desirable to connect an air feed drill to its pneumaticpressure source by a hose running to the back head or rear end of thedrill where the hose is least likely to interfere with the use of thedrill. This rear end location of the hose connection creates a problemin double-acting drills, which are reciprocated back and forth byalternately admitting fluid pressure into a pair of piston chambers inthe tool, because it necessitates the provision of the tool with an airpassage running to the front piston chamber around the piston.Heretofore, this front piston chamber passage generally has been locatedin the casing of the tool which is a disadvantage because it requiresthe thickness of the casing, and, consequently, the diameter of thetool, to be larger than it would be it the passage were eliminated andit creates manufacturing problems which are difficult to solve.

The principal object of this invention is to eliminate the need for theundesirable passage in the tool casing running to the front pistonchamber and, therefore, to reduce the casing thickness and the overalldiameter of the tool, thus rendering the tool smaller, easier to handleand to operate and more economical to manufacture.

Other important objects include: to provide a simplified valve mechanismfor alternately admitting pneumatic pressure to the piston chambers of adouble-acting air feed drill; to provide a double-acting air feed drillwhich is automatically retracted when air pressure is vented from itsrear piston chamber; to provide a piston chamber vent valve which iseffective to vent the piston chamber at low pressures and is actuated byhigh pressure to close and discontinue venting the piston chamber; andto provide an air feed drill which is double-acting and does not need oruse a separate passage running from the rear end of the tool to thefront piston chamber.

The invention is illustrated in the accompanying drawings wherein:

FIG, 1 is a diagrammatic view of the fluid control system of an air feeddrill incorporating the features of this invention and shows the drillbeing fed forwardly;

FIG. 2 is similar to FIG. 1 and shows the control valve of the fluidcontrol system in its alternate position, with the drill beingretracted;

FIG. 3 is a longitudinal section of the rear half of the air feed drill;

FIG. 4 is a broken and cut-away elevational view of the air feed drillof this invention;

FIG. 5 is an enlarged section taken on line 55 in FIG. 4 and havingportions cut-away;

FIG. 6 is a fragmentary section taken along the line 6-6 in FIG. 5;

FIG. '7 is an enlarged fragmentary view of a portion of FIG. 3; and

PEG. 8 is an enlarged fragmentary View of another portion of FIG. 3.

The air feed drill shown in the drawings comprises a body 1 formed by anelongate cylinder 2 which is open at its front end and closed at itsrear end by a back head 3,i@5,h53 Patented July 20, 1965 3. A piston 5is axially slidable in the cylinder 2 and includes a hollow piston rod 6which extends forwardly from the piston 5 through an annular ring 7mounted in [the front end of the cylinder 2.

The foregoing structural arrangement forms two fluidreceiving chamberswhich are separated by the piston S and are adapted to alternatelyreceive fluid pressure, such as pneumatic pressure, for feeding thepiston Sin alternate directions in the inner cylinder 2. The chamberlocated rearwardly of the piston 5 is designated the forward fee-dchamber 8 and the chamber located in front of the piston 5 is designatedthe retraction chamber 9.

The front end of the piston rod 6 is fixed to the rear end of aconventional vane-type air motor 12 which is slidably mounted in thefront half of the forward portion of the cylinder 2. The air motor 12carries a conventional drill chuck l3 projecting forwardly from thefront end of the body 1. Normally, the drill chuck is driven through aset of planetary gears (not shown) which are located between the airmotor 12 and the drill chuck 13 and reduce the rotary speed of the airmotor 12 to a suitable value for driving the chuck 13. No attempt ismade to describe the air motor and drill chuck further since these itemsare conventional and well known in the air feed drill art, as shown bythe U.S. patents to Taylor, 2,674,098, Robinson, 2,857,789, and DeGroff, 2,860,531.

From the foregoing, it will be obvious that the air motor 12 rotates itsdrill chuck 13 while the piston 5 axially feeds the motor 12 and chuck13 through a reciproca-tory cycle during a work operation. Thisreciprocatory cycle begins and terminates with the piston 5 resting atthe rear end of its travel path and includes a forward stroke followedby a-return stroke.

Motor fluid circuit A simplified version of this circuit is shown inFIG. 1. In general, it includes a fluid pressure source (not shown)feeding a main line 15 connected to a conventional threeway valve 16.The valve 16 is connected by a hose 17 (shown in FIG. 3) to a fluidinlet passage 18 in the back head 3. The inlet passage 18 opens into atube 19 which is fixed on the front of the back head 3 and extendsforwardly through the piston 5 and the piston rod 6. The piston rod 6 ishollow and forms a central rod passage 25 which opens at its front endinto the fluid inlet 21 of the air motor 12.

Access of the fluid pressure from the tube 19 into the central rodpassage 2%) in the piston rod 6 is determined by .a motor valve 22 whichis mounted in the central rod passage 20 and is located to seat on andclose the front end of the tube 19 when the piston 5 is fully retracted.As the piston 5 starts its forward stroke, as shown in FIG. 1, the motorvalve 22 is lifted off the front end of the fixed tube 1% and the fluidpressure in the tube 19 is free to flow into the rod passage 2b to theair motor 12, thereby driving the motor 12 and its chuck 13. Thisdriving of the motor 12 continues throughout the remainder of the cycleand is only stopped when the piston 5 returns and seats the motor valve22 once again on the front end of the fixed tube 19.

The specific construction and mounting of the motor valve 22 is shown inFIG. 3. A follower rod 25 is anchored at its front end to the front endof the piston rod s and extends axially rearwardly through the centralrod passage 25 the fixed tube 19 and slidably through the back head 3 toproject behind the back head a substantial distance. This follower rod25 is smaller than the rod passage 2% and the interior of the fixed tube19 so that fluid may pass therebetween. Suitable seals circle thefollower rod 25 at the rear of the back head 3 to prevent the pressurefluid from leaking rearwardly from the fixed tube 19.

The motor valve 22 carries a resilient rear face 26 adapted to seat onthe front end of the fixed tube, is slidably mounted on the follower rod25 for limited movement and is springbiased rearwardly by a spring 27which is anchored at its front end to the follower rod 25. Thisarrangement insures that the motor valve 22 is firmly seated against thetube 19 when the piston is retracted and compensates for any variationbetween the pistons position when it is fully retracted and when themotor valve 22 is seated. The foregoing structure is disclosed in thepreviously mentioned copending U.S. patent application of John M. Clappet al.

Piston fluid circuit FIG. 1 shows a portion of the back head 3 separatefrom the body 1 to simplify the illustration of the fluid circuits ofthe tool. It will be understood that FIG. 1 is merely a diagrammaticview and does not show the true construction or locationof the back head3 and its associated elements.

The back head 3 is provided with a two-position spool valve 30 whichslides in a bore 31 formed in the back head 3. In one position, itsfront position shown in FIG. 1, the spool valve 30 feeds fluid pressureto the forward feed chamber 8 to drive the piston 5 on its forwardstroke, and in its other position, its rear position shown in FIG. 2,the spool valve 30 exhausts the forward feed chamber 8 so that thepiston 5 can be driven rearwardly through its return stroke.

The spool valve 30 is biased forwardly in the bore 31 by a spring 32.When the spool valve 30 is in its forward position, as shown in FIG. 1,the front and rear chambers 33 and 34 located at the opposite ends ofthe valve 30 are in communication with the fluid pressure in the inletpassage 18 by means of the intermediate passages 35 and 36. The frontintermediate passage 35 is normally in direct communication with thefront chamber 33 and the rear intermediate passage 36 communicates withthe rear chamber 34 by means of a small port 37 in the spool valve 30.

When the spool valve 30 is in its forward position, the admission offluid pressure into the inlet passage 18 results in the simultaneousadmission of fluid pressure to both the front and rear chambers 33 and34 of the valve, which prevents the creation of a differential pressurebe tween the two chambers 33 and 34. Hence, the spool valve 30 remainsin its forward position. The spring 32 normally moves and holds thespool valve 30 in its forward position when the fluid pressure is closedoff from the tool.

After fluid pressure is admitted to both the front and rear valvechambers 33 and 34, the spool valve 30 is moved to its rear position byventing the rear chamber 34, thus creating a pressure differentialbetween the two valve chambers tending to drive the valve rearward-1y.This venting of the rear chamber 34 is accomplished by pushing inwardlyon the poppet valve 38 located at the rear end of the bore 31 andprojecting from the rear end of the back head 3. The poppet valve 38 isloosely mounted in its guide hole 39 so that when its head 40 is pushedinwardly off its seat, the fluid pressure in the rear chamber 34 freelyescapes to the atmosphere along the clearance space between the valvestem and its guide hole. valve since it actuates the spool valve 30 toits rear position, causing the piston 5 to move along its return stroke.

When the spool valve 30 is in its rear position, it is moved back to itsforward position by exhausting the front valve chamber 33, allowing thespring 32 to drive the spool valve 30 forward. Exhausting the frontchamber 33 may be accomplished by momentarily shutting off the the fluidpressure to the tool and exhausting the inlet passage 18 by means of theconventional three-way valve 16 shown in FIG. 1.

Exhausting the front valve chamber 33 may also be The poppet valve 38 istermed a reversing poppet accomplished by a poppet valve 41, which islocated on the side of the back head 3. The poppet valve 41 is similarto the poppet valve 38 and is mounted in the back head 3 to reciprocatein a cavity 42 which communicates with the chamber 33 through a passage43. When the valve 41 is depressed, it simultaneously plugs the end ofthe passage 35, opening into the cavity 42, and exhausts the cavity 42which is in communication with the front chamber 33. The poppet valve 41is termed a manual recycle valve since it can be used to cause the toolto begin a cycle, as will be clear later.

Forward feed piston stroke When the spool valve 30 is in its forwardposition as shown in FIG. 1, it allows pressure fluid to flow from therear intermediate passage 36 to a forward stroke passage 45 running to aforward stroke needle valve 46. The needle valve 46 meters the fluidpressure and dumps it into a passage 47 leading into the forward feedchamber 8.

Also, in the forward position of the spool valve 39, the retractionchamber 9 is exhausted by a pressure-actuated vent valve 49 located atthe front end of the chamber 9 and formed in part by the annular ring 7,as seen in FIG. 8. The annular ring 7 is slidab-ly mounted in thecylinder 2 and rests against a spring 53 located between its front faceand a washer 51 seated against a lock ring 52 fixed in the interior ofthe cylinder 2. Normally, the spring 50 prevents the ring 7 from movingforwardly beyond a predetermined position in the cylinder 2. Thecircumference of the ring 7 is encircled by an O-ring 53 and theinterior of the cylinder 2 is formed with an annular groove 54 locatedto loosely contain the O-ring 53 when the ring 7 is in its normalpredetermined position in the cylinder 2.

The vent valve 49 operates in the following manner. When the fluidpressure in the retraction chamber is relatively low, the ring 7 is heldin its normal position where in the O-ring 53 is spaced from the wallsof the groove 54, resulting in the chamber 9 being vented to atmospherepast the O-ring 53 and out the front end of the cylinder 2. Sufficientspace exists between the cylinder 2 and the air motor 12 to provide avent path therebetween.

When the pressure in the retraction chamber is high, as in FIG. 2, thering 7 is pressed forwardly to overcome the spring 50 and to press theO-ring 53 against a wall of the annular groove, thus closing the ventvalve 49 and sealing the retraction chamber 9 from the atmosphere. Inbrief, when the pressure on the vent valve 49 is relatively low, it isopen, and when the pressure is high, it is closed.

Return piston stroke The follower rod 25 extending from the rear of theback head 3 carries at its rear end a bracket 56 containing a threadedbolt 57. As the piston 5 carries the fol lower rod 25 forwardly duringthe forward stroke of the piston,the bolt 57 eventually strikes anddepresses the reversing poppet valve 38. The point in the forward strokeat which the reversing poppet valve 38 is depressed can be varied merelyby adjusting the threaded bolt 57. Hence, the length of the forwardpiston stroke is adjusted by means of the bolt 57.

As previously explained, the depression of the reversing poppet valve 38exhausts the rear valve chamber 34 to create a pressure differentialbetween the front and rear valve chambers 33 and 34 and cause the spoolvalve to move to its rear position.

When the spool valve 30 is in its rear position as shown in FIG. 2, itexhausts the forward feed chamber via the passage 47. The passage 47 isplaced in communication with a vent passage 59 by a peripheral groove 60on the spool valve 30.

It will be noted that with the spool valve 30 in its rear position, itcloses off the rear intermediate passage 36 with the forwardstrokepassage 45, and the exhaust of the forward feed piston chamber 8bypasses and is Q not metered by the forward stroke needle valve 46.Instead, the vent passage 59 is connected by a needle valve 61 to a ventport 62 and the needle valve 61 is used to adjust and meter the exhaustof the forward feed piston chamber 8.

When the forward feed chamber 8 is exhausted, pressure is automaticallyfed to the retraction chamber 9 by means of a lost motion valve 64connecting the piston to the piston rod '6, as seen in FIG. 7. Thepiston 5 includes a short nipple '65 projecting forward telescopicallyinto the rear end of the piston rod \6 and held in the rod 6 by a lockball on resting in a radial hole in the nipple 65 and in an annulargroove67 formed in the interior of the piston rod 6. The groove 67 issufficiently wide to allow the rod 6 to slide back and forth on thenipple 65 for a short distance between a position wherein the rear edgeof the rod 6 seats against a valve seat 68 mounted on the front face ofthe piston 5 and a position spaced from the seat 68.

The operation of the lost motion valve 64 should now be obvious. whenthe pressure in the forward drive chamber 8 is high, the piston 5 isbiased forward to press the valve seat 68 against the end edge of thepiston rod 6 thus closing the lost motion valve 64. When the pressure inthe forward drive chamber 8 is exhausted, the high pressure existing inthe passage 20 of the piston rod 6 forces the piston 5 rearwardly on therod 6, thus lifting the valve seat 6% off the end of the rod 6 andopening the lost motion valve to allow the pressure in the central rodpassage 26 to flow into the retraction chamber 9. Sufficient clearanceis provided between the nipple 65 and the interior of the rod 6 to allowpressure to flow freely therebetween.

When the piston 5 reaches the end of its return stroke, it stops andremains in that position so long as the spool valve 39 remains in itsrear position, as shown in FIG. 2. The spool valve 3t will remain in itsrear position so long as fluid pressure is maintained in the front valvechamber 33.

In order to recycle or start another cycle of the tool, the front valvechamber 33 is exhausted using either the three-way valve 16 or themanual recycle poppet valve 41, as previously explained. The manualrecycle poppet valve 41 is normally used when the operator is using thedrill by itself, instead of in a gang of tools. When the tools are usedin a gang, they are usually controlled by the valve 16 which momentarilyshuts off the fluid pressure to the tools and exhausts the feeding hoses17 leading from the valve 16 to the individual tools. This feature ofbeing able to recycle the tools simply by interrupting the fluidpressure supply is highly desirable as it enables the use of only onehose for both supplying fluid pressure to and controlling the tools.

Miscellaneous structure FIG. 3 illustrates as set of leaf springs 71)mounted in the cylinder 2 in front of the lock ring 52. These leaf orfinger springs 79 extend radially inward and have their inner endscurving forwardly. The leaf springs '70 are adapted to engage ahead ofan enlarged bulge 71 on the piston rod 6 to hold the piston 5 in itsrearwardly retracted position when the tool is not energized with airpressure.

The projecting portion of the follower rod 25 and the bolt 57 whichoperates the reversing poppet valve 38 are surrounded and substantiallyenclosed within a sleevelike guard 72 to prevent an operator from beingaccidentally injured by these moving parts.

Operation Prior to the start of operation of the air feed drill, andprior to the admission of fluid pressure to it, the piston 5 is locatedat the rear end of its reciprocatory travel path and the spool valve 3%is resting in its forward position. Since the piston 5 is in itsrearrnost position, the motor valve 22 in the piston rod passage 2!] isseated on and closes the fixed tube 19 extending axially forward fromthe back head 3.

\Fluid pressure is fed to the tool simply by turning the valve 16 to theposition shown in FIG. 1, thus introducing fluid pressure into the inletpassage 18 in the back head 3. This fluid pressure is simultaneously fedto both the front and rear chambers 33 and 34 of the spool valve 30, viathe intermediate passages 35 and 36, causing the spool valve 39 toremain in its forward position.

In the forward position of the spool valve 30, the fluid pressure flowsfrom the rear intermediate passage 36 past the spool valve 30 and intothe forward stroke passage 45. The passage 45 dumps the fluid pressureinto the forward stroke needle valve 46 which meters it and feeds it viathe passage 47 into the for-ward feed piston chamber 8, resulting in thepiston 5 being driven forward on its forward stroke. During the forwardstroke of the piston 5, the retraction piston chamber 9 is exhausted bythe vent valve 49 which is held in its rearmost position by the spring56, i.e., the pressure in the retraction chamber 9 is not high enough toovercome the spring iii and bias the valve 49 to a closedposition.

During the initial portion of the forward stroke of the piston 5, themotor valve 22 is lifted off the end of the fixed tube 19 to allow fluidpressure to flow to the motor 12, which begins to drive the chuck 13 andwhatever tool bit it may be holding. Hence, the chuck '13 issimultaneously rotated and fed axially forward on its forward stroke.The speed of the forward stroke may be controlled by adjusting theneedle valve 46.

As the piston 5 moves on its forward stroke, the follower rod 25 carriesthe threaded bolt 57 forward until it eventually engages and depressesthe reversing poppet valve 38. Depression of the valve 33 vents the rearchamber 34 of the spool valve 39 causing the pressure in the forwardvalve chamber 33 to drive the spool valve 30 to its rear position, asshown in FIG. 2.

In the rear position of the spool valve 30, it blocks the forward strokepassage 45 and exhausts the forward feed chamber 8 to atmosphere via thepassage 47, the peripheral groove 6%} in the spool valve 36), the ventpassage 59, the needle valve 61 and the vent port 62. The needle valve61 can be adjusted to vary the speed of the return stroke of the piston5.

When the forward feed chamber 8 is exhausted, the fluid pressure in thecentral rod passage 26 acts to move the piston 5 rearwardly from the endof the piston rod 6, thus opening the lost motion valve 64 and admittingfluid pressure from the central rod passage 24? into the retractionchamber 9. The relatively high pressure (about psi.) of the fluidadmitted to the retraction chamber 9 causes the vent valve 5$ to close,thus sealing the retraction chamber from atmosphere, and drives thepiston 5 on its return stroke.

As the piston 5 stops at the rear end of its return stroke, the motorvalve 22 seats on and closes the front of the fixed tube 19 thusshutting off fluid pressure to the rotary motor 12 and stopping itsoperation. The spool valve 36 will thereafter remain in its rearposition until it is desired to recycle the tool for another operation.

Recycling the tool can be accomplished in either of two ways, bydepressing the manual recycle poppet valve 41 or by momentarily closingoff the fluid pressure from the tool by operating the three-way valve16. The use of either of these expedients results in the exhaust offluid pressure from the front valve chamber 33, thus allowing the spring32 to drive the spool valve 3t) back to its forward position.Thereafter, when fiuid pressure is again admitted to the tool bymanipulating the three-way valve 16 or by closing the recycle poppetvalve 41, the tool beings another forward stroke. The followingoperation of the cycle is identical with the description of theoperation of the preceding cycle.

Although a preferred embodiment of the invention has 7 been illustratedand described in detail, it will be understood that the inventioncontemplates other embodiments and variations of the basic invention.

Having described our invention, we claim:

1. A fluid-operated tool for rotating and axially reciprocating a toolimplement, said tool comprising: a tool body; a piston slidably mountedin said body for axially reciprocating movements therein and carrying afluid-operated motor and a spindle on its front end; said tool bodycontaining a pair of piston chambers separated by said piston andadapted to receive fluid pressure alternately for reciprocating saidpiston, said pair of piston chambers including a forward feed chamberand a retraction chamber; exhaust means operative to normally exhaustsaid retraction chamber when the pressure in the retraction chamber islow and operative to seal the retraction chamber when the pressure inthe retraction chamher is high; and valve means connected to said pistonchambers for admitting fluid pressure alternately into said pistonchambers.

2. The fluid-operated tool of claim 1 wherein said valve means includesmeans operative to automatically admit pressure fluid into saidretraction chamber in response to the exhaust of pressure fluid fromsaid forward feed chamber.

3. The fluid-operated tool of claim 2 wherein: said piston includes ahollow piston rod connected to the motor and conveying fluid pressure tosaid motor; and said valve means includes a lost motion connectionbetween said piston and piston rod which automatically opens to admitpressure from inside the piston rod to said retraction chamber when saidforward feed chamber is exhausted.

4. The fluid-operated tool of claim 3 wherein said valve means includes:a first needle valve connected to the forward feed chamber and beingadjustable to meter the fluid pressure being admitted to saidforwardfeed chamber; and a second needle valve connected to said forward feedchamber and being adjustable to meter the fluid being exhausted fromsaid forward feed chamber, whereby the needle valves control the speedof the forward feed stroke and the return stroke of the pistonindependently of each other.

5. The fluid-operated tool of claim 1 wherein said exhaust means for theretraction chamber includes: a valve body movably mounted in theretraction chamber and adapted to be moved in one direction from anormal position to an alternate position by pressure in the retractionchamber; a resilient means biasing the valve body in the other directionopposite to the pressure in said retraction chamber; and said tool bodycontaining a vent which is open for exhausting said retraction chamberwhen said valve body is in its normal position and closed when the valvebody is in its alternate position.

References Cited by the Examiner UNITED STATES PATENTS 2,081,931 6/37Hulfrnan 173-152 2,604,759 7/52 Smith 173155 2,674,098 4/54 Taylor Q173155 3,041,897 7/62 Linsker 7733.5

BROUGHTON G. DURHAM, Primary Examiner.

1. A FLUID-OPERATED TOOL FOR ROTATING AND AXIALLY RECIPROCATING A TOOLIMPLEMENT, SAID TOOL COMPRISING: A TOOL BODY; A PISTON SLIDABLY MOUNTEDIN SAID BODY FOR AXIALLY RECIPROCATING MOVEMENTS THEREIN AND CARRYING AFLUID-OPERATED MOTOR AND A SPINDLE ON ITS FRONT END; SAID TOOL BODYCONTAINING A PAIR OF PISTON CHAMBERS SEPARATED BY SAID PISTON ANDADAPTED TO RECEIVE FLUID PRESSURE ALTERNATELY FOR RECIPROCATING SAIDPISTON, SAID PAIR OF PISTON CHAMBERS INCLUDING A FORWARD FEED CHAMBERAND A RETRACTION CHAMBER; EXHAUST MEANS OPERTIVE TO NORMALLY EXHAUSTSAID RETRACTION CHAMBER WHEN THE PRESSURE IN THE RETRACTION CHAMBER ISLOW AND OPERATIVE TO SEAL THE RETRACTION CHAMBER WHEN THE PRESSURE INTHE RETRACTION CHAMBER IS HIGH; AND VALVE MEANS CONNECTED TO SAID PISTONCHAMBERS FOR ADMITTING FLUID PRESSURE ALTERNATELY INTO SAID PISTONCHAMBERS.